Hello i am new to revolvers and this happens to be my first post so please bare with me. I just picked up what I think is a 5 screw k frame pre model 10 military and police 38spl but I'm not sure. Do I measure from the cylinder to end of barrel or does measurements start at end of frame to get barrel length???? S/n number is 512469 any information on date and value would be awsome thanks